This invention relates to a can lid with a push-in tear tab. It relates more particularly to a one-piece lid having a tab which can be pushed down into the container to form a pour opening in the lid without separating from the lid.
1. Field of the Invention
The lids of the type with which we are concerned are used to form the top walls of cans or other containers for a variety of different products such as beverages, powdered or granualted materials and the like which may be maintained in the container at or above atmospheric pressure. The invention is particularly applicable to lids for cans containing carbonaedj beverages.
2. The Prior Art
A pre-examination search developed the following references:
Asbury--U.S. Pat. No. 3,246,791--April, 1966 PA0 Asbury--U.S. Pat. No. 3,355,058--November, 1967 PA0 Klein--U.S. Pat. No. 3,779,417--December, 1973 PA0 Perry--U.S. Pat. No. 3,843,011--October, 1974 PA0 Perry--U.S. Pat. No. 3,952,912--April, 1976 PA0 Perry--U.S. Pat. No. 4,062,471--December, 1977 PA0 Asbury--U.S. Pat. No. 4,078,693--March, 1978 PA0 Gynp, et al.--U.S. Pat. No. 4,078,694--March, 1978 PA0 Perry--U.S. Pat. No. 4,084,721--April, 1978 PA0 Amberg et al.--U.S. Pat. No. 4,210,256--July, 1980 PA0 Rossetti--U.S. Pat. No. 4,377,244--March, 1983
Container lids with integral tear tabs for forming pour openings in the lids are well known in the prior art including the patents identified above. Until the last few years, the most prevalent type of tear tab lid for beverage containers consisted of a two-piece construction having a finger-operated pull ring riveted to a portion of the lid delineated by a tab-defining score line. When the user pulls the ring away from the can, the ring and tab separate from the remainder of the lid thereby forming a pour opening in the lid for the container contents. The torn out tab is a metallic curl with sharp edges and is often carelessly disposed of creating a visual nuisance and a safety hazard. Also, that two-piece lid is relatively expensive to make involving, as it does, the riveting of a pull ring to the lid per se.
In an effort to respond to the objections raised against the aforesaid containers with separable tear tabs, a container lid was designed with a leverage ring that, when lifted, pushed a scored, tab-defining area of the lid into the interior of the container to form a pour or drink opening, with both the tab and the leverage ring remaining attached to the lid. An example of this type of container lid is disclosed in the above-identified U.S. Pat. No. 4,084,721 and the related references identified therein. While this lid solved the environmental problems associated with lids with separable tear tabs, it has not cut costs because it still requires the riveting of a separate leverage ring to the can lid.
It is only relatively recently that serious efforts have been made to develop a container lid with an integral tear tab scored into the lid which can be pushed in by the user's finger to form a drink or pour opening in the lid while remaining attached to the lid, examples of same being disclosed in the above-identified patents U.S. Pat. Nos. 4,078,694 and 4,377,244.
In the most common form of push-tab lid construction, an opening is formed in the lid which is closed by an integral tab hinged to the lid, the scored joint between the tab and the remainder of the lid being sealed on the inside by a plastic sealant material. As these containers often contain a carbonated beverage, there is substantial internal pressure acting against the underside of the tab. Consequently, the tab is usually made larger than the opening in the lid so that its edge margin engages under the lid to prevent the tab from being pushed out by the internal pressure.
Usually also, to facilitate pushing in the tab, the lid includes a smaller vent hole closed by a similar integral tab which can be pushed in to relieve the internal pressure before the larger tab is depressed to open the pour opening in the lid. This type of construction, however, has certain disadvantages militating against its wider use. More particularly, the consumer must be educated as to the correct way to open the can by pushing in the vent tab before the pour tab. This means that special instructions must be applied to the can for this purpose. Even then, two separate operations are required to open the container properly which is annoying to certain consumers.
Still further, the consumer must push down with his finger with a considerable force on the pour tab which is about the same size as the end of the finger before that tab will separate along its score line from the remainder of the lid. The exerting of the requisite force may be a problem for certain aged or infirm individuals. Most importantly, when the consumer does succeed in pushing in the pour tab, that tab tends to give way suddenly so that the consumer's finger often thrusts down into the pour opening where it can be cut by the sharp scored edge of that opening. Prospective purchasers perceive this unsanitary and dangerous potential which therefore inhibits consumer acceptance of the product. The only prior solution to that problem known to applicants involves folding back the edge of the opening on itself to round off the edge. However, that requires a separate forming operation on the lid which increases its overall cost.